Effectiveness and safety of PRP on persistent olfactory dysfunction related to COVID-19.

INTRODUCTION: Olfactory dysfunction (OD) is a well know symptom of coronavirus disease 2019 (COVID-19), accounting for 48 to 85% of patients. In 1 to 10% of cases, patients develop a chronic olfactory dysfunction (COD), lasting more than 6 months. Recently, platelet-rich plasma (PRP) was used in patients with non-COVID-19 COD and authors reported encouraging results. METHODS: In the present study, we investigated the usefulness and safety of PRP injection in 56 patients with COVID-19 COD by the Sniffing Stick test (TDI score) and a linker-scale from 0 (none) to 3 (strong) and we compare the result to a control group. RESULTS: At 1 month post-PRP injection, the mean TDI scores significantly improved by 6.7 points in the PRP group (p < 0,001), the mean self-assessment of improvement in smell function was 1.8 (mild-to-moderate) in the PRP group, which was significantly higher than the score (0.3) in the control group (p < 0,001). CONCLUSION: Our results showed that PRP in the olfactory cleft can increase the olfactory threshold 1 month after the injection. Moreover, our results suggest that timing of treatment may be an important factor and that PRP is a safe treatment, because no adverse effects were reported throughout the study. TRIAL REGISTRATION NUMBER: NCT05226546.

Efficacy and safety of oral corticosteroids and olfactory training in the management of COVID-19-related loss of smell.

PURPOSE: As the COVID-19 pandemic continues, an increasing number of patients are afflicted by olfactory loss, a now well-recognized symptom of the disease. Though many patients seem to recover their sense of smell after a few weeks, a certain proportion of them seem to develop long-lasting olfactory disorder. Yet, as of October 2020, there is no recommended standardized treatment to reduce the risk of developing long-term olfactory disorder. In this pilot study, we investigated the efficacy and the safety of oral corticosteroids and olfactory training as a treatment for patients with persistent olfactory dysfunction as a result of COVID-19. METHODS: Non-hospitalized patients with a sudden loss of smell and a confirmed COVID-19 diagnosis were recruited by hospital call from February to April 2020. These participants were submitted to an extensive psychophysical testing in order to identify those with persistent dysosmia. Dysosmic patients were then treated either by a 10-day course of oral corticosteroids combined with olfactory training, or by olfactory training alone. All participants were subject to a second olfactory test after a mean of 10 weeks. RESULTS: 72 subjects with documented COVID-19 infection performed the initial olfactory test, on average 5 weeks after losing their sense of smell. Amongst them, 27 (37.5%) patients showed persistent dysosmia and were all included in this study. Nine participants received oral corticosteroids and performed olfactory training (OCS + OT), while 18 performed olfactory training (OT) only. Only participants in the OCS + OT group had significantly improved their olfactory score and did so above the minimal clinically important difference for subjective improvement of smell (p = 0.007). Three of the participants who received oral corticosteroids reported minimal and transient side effects. CONCLUSION: This pilot study may suggest the combination of a short course of oral corticosteroids and olfactory training is safe and may be beneficial in helping patients with enduring dysosmia recover from olfactory loss due to COVID-19. There is a crucial need for further investigation with larger cohorts to corroborate these findings.

Psychophysical evaluation of chemosensory functions 5 weeks after olfactory loss due to COVID-19: a prospective cohort study on 72 patients.

PURPOSE: To evaluate the evolution of chemosensation via extended psychophysical testing in patients who suffered from sudden chemosensory loss due to coronavirus disease 2019 (COVID-19). Additionally, this study sought to determine whether odor threshold testing provided additional information on olfactory loss due to COVID-19 compared to the more common odor identification testing. METHODS: Prospective cohort study of patients with sudden chemosensory loss since February 2020 and confirmed COVID-19 infection via RT-PCR or serology testing. Olfactory function was tested extensively using the "Sniffin Sticks" test battery. In addition, we screened gustatory perception and nasal cooling sensations using psychophysical tests. RESULTS: Seventy-two patients completed the study. After a mean of 37 days, 37% of patients showed olfactory dysfunction, 7% were dysgeusic, and 48% showed signs of low sensitivity for cooling sensation. A longer duration of anosmia before smell improvement was correlated with lower olfactory function at 5 weeks. Odor threshold detection was more affected by COVID-19 compared to odor identification. CONCLUSION: Five weeks after developing sudden chemosensory loss due to COVID-19, a high proportion of patients were dysosmic and showed signs of low nasal cooling sensitivity, whereas most of them had normal taste function. SARS-CoV-2 affected mainly odor thresholds, possibly suggesting that the major cause of loss of smell lies at the level of the olfactory neuroepithelium, rather than in the central nervous system.